Light controlled apparatus



1943- D, PARSON, JR 2,336,633

I LIGHT CONTROLLED APPARATUS Filed Jan. 24, 1942 60 whmajIW ISnnentor flo/vALa pmso/v JR.

Wm (Ittorneg Patented Dec. 14, 1943 UNITED STATES PATENT OFFICE Claims.

This invention relates to light controlled mechanism, and, more specifically,- is concerned with apparatus for firing a photo-flash bulb substantially in synchronism with the flash of another remotely positioned photo-flash bulb.

Heretofore, it has been the standard practice when photographing a large group, room, or other subject under adverse light conditions to employ one photo-flash bulb adjacent or on the camera and to position one or more additional flash bulbs at points throughout the room, which additional fiash bulbs are connected by extension cords in the same electrical circuit as the flash bulb adjacent or on the camera. Thus, when the shutter of the camera is opened an electric switch is simultaneously closed to supply electric current to the various photo-flash bulbs so that they are fired in synchronism with the operation of the camera shutter.

However, it is often a nuisance and inconvenience to stretch the electric cord extensions around the room, the cords may be tripped over, or appear in the picture, and it is sometimes impossible to stretch the cords to properly position the supplementary flash bulbs. Further, in operating with long extension cords there is often suflicient voltage drop and lag due to the resistance and reactance of the long extension cord that the usual small voltages employed will not give true synchronization of remotely positioned photo-flash bulbs. Efforts to achieve by radio means synchronization of firing of photo-flash bulbs positioned at a considerable distance to each other, have not been successful commercially because of the very expensive equipment involved and because of the necessity to incorporate therein standard relay actuated mechanisms which have such a time lag as to destroy the synchronization of the firing of the flash bulbs. Further, in such radio controlled synchronization apparatus misflring may occur because of electrical interference due to street cars, motors, or other means.

It is the general object of my invention to avoid and overcome the foregoing and other difiiculties and objections by the provision of portable apparatus which is adapted to fire a photo-flash bulb in synchronism with a photofiash bulb fired at a spot remote from the apparatus.

Another object of my invention is to provide apparatus of the character described and including a photo-electric cell, an amplifier, and a sensitivity control whereby the apparatus can be quickly adjusted to respond to any desired, character 6f light control therefor.

Another object of my invention is the provision of light controlled apparatus of self contained character which is portable, light in weight, readily positioned, adjusted and operated and is relatively inexpensive to manufacture and keep in operation.

Another object of my invention is to provide an apparatus of the type described including a photo-electric cell positioned in a shielded aiming device having a long tube, the device being adjustably mounted on a ball and socket support whereby the tube can be pointed in a given direction to pick up light impulses from that direction and from no other.

Another object of my invention is the provision of an improved relay combination for eliminating has.

The foregoing and other objects of my invention are achieved by the provision of a photoelectric cell, an amplifier having its input connected to the output of the photo-electric cell and a photo-flash bulb associated with the output of the amplifier so that when the photoelectric cell device picks up a suitable light radiation, as from the flash of a photo-flash bulb, the photo-flash bulb associated with the output of the amplifier will be fired substantially in synchronism with the light impulse picked up by the photo-electric cell.

For a better understanding of my invention reference should be had to the accompanying drawing wherein Fig. 1 illustrates diagrammatically an apparatus embodiment of my invention; Fig. 2 is a schematic wiring diagram of one form of the invention; and Fig. 3 is a longitudinal cross sectional view through the photo-electric cell aiming device which may be incorporated with my invention.

As above indicated, my invention broadly is concerned with the use of a photo-electric cell pick-up device, an amplifier connected to the output of the photo-electric cell, and a photoflash bulb associated with the output of the amplifier. Thus, in Fig. 1 of the drawing the nu- I meral l0 indicates generally a photo-electric decation with a long tube 26 which prevents light from any source other than that desired from striking the photo-electric cell 20. In fact, the aiming device thus provided may include sights 28- and 30, and the case 22 and tube 26 is generally supported upon a ball and socket joint 32 tightened by a thumb nut 34 so that the tube ZB-can be sighted and clamped to extend towards the desired source of light.

A spring clip 36 of known type and having the usual rubber covered jaws 38 conveniently supports the ball and socket joint 32 so that the entire photo-electric device Hi can be readily clamped to any suitable support. Often it is handy to mount the ball and socket joint 32 directly upon the case of the amplifier l4. Again, although I have found that the shielding and aiming device just described is preferable when high sensitivity is desired, particularly when varying or unexpected light conditions may be encountered, nevertheless, I have found that the aiming tube and even the shielding means may often be eliminated under conditions of lower sensitivity. Specifically, the photo-electric cell may be incorporated with the case of the amplifier I, either by mounting in a suitable socket thereon, or by plugging a cable into the socket with the cell carried at the end of the cable. A very convenient manner of incorporating the photo-electric cell with the apparatus is to position the cell inside the case with an opening in the side of the case through which the light may pass to strike the cell. I

It is sometimes advisable to incorporate an impedance matching transformer between the amplifier I4 and the photo-flash bulb l8. The impedance matching transformer has been diagrammatically indicated by the numeral 42. No impedance matching means need be employed where the relative impedance is not grossly out of line, as is the case of the input side of the amplifier, all of which will be understood by those skilled in the art. The impedance matching transformer 42 also serves to isolate the flash bulb from the no signal D. C. plate current, and takes the high voltage oil the lamp, eliminating any danger of shock.

The photo-flash bulb I8 usually is carried in a reflector which in turn is supported by a spring clamp 46 of standard type having rubber covered jaws l8.

Specifically, my invention takes two distinct embodiments. First, I may connect the photofiash bulb i8 directly across the output of the amplifier l4 so that the increased output of the amplifier will fire a photo-flash bulb when the photo-electric cell connected to the input of the amplifier picks up a light impulse. In this embodiment of my invention the amplifier I! may be of the type adapted to be plugged into a standard 110 volt electric outlet, or the amplifier may be of a self contained battery operated type. The details of the amplifier are not important so long as sumcient gain is provided, but it should be of the power rather than the voltage type, and usually the amplifier is of the class-A31 or the class-AB: type. The type of amplifier usually used in public address work is satisfactory. A class B power audio amplifier may also be employed inasmuch as distortion is not important.

I "have found. that when coupling the photofiash bulb l8 directly to the output of the standard power amplifier, as just described, that it is possible to prevent the firing of the photo-flash bulb even though thephoto-electric cell is subjected to a constant source of light of considerable brilliancy. It requires an oscillating (i. e., an increasing and decreasing) light source to fire the photo-flash bulb connected to the output of the amplifier. For example, if a flashlight of considerable brilliancy is pointed directly at the photo-electric cell the photo-flash bulb connected to the output of the amplifier will not be fired, however, if the flashlight is fiicked on and of! of the photo-electric cell the photo-flash bulb will be fired. This is an important characteristic of the apparatus of my invention already specifically described and employing the standard amplifier. It makes it possible to use the apparatus in a room having considerable illumination, but of a steady or constant character. The apparatus is, none the less, very sensitive to an oscillating or varying light source, that is one which changes in brilliancy, such as that created by the firing of a photo-flash bulb.

I have found that in operating apparatus of the embodiment of the invention just described that a photo-flash bulb positioned adjacent or on the camera will fire the photo-flash bulb l8 at a distance of as much as 150 feet or more and that the flash bulb l8 will be fired so nearly in synchronism with the flash bulb adjacent or on the camera that I have been unable to discover a time lag. The apparatus will function in the indicated manner even though electric or other steady illumination is present.

The second embodiment of my invention is illustrated in Fig. 2, and wherein the photo-flash bulb, indicated at l8a, is associated with the output of the amplifier in a somewhat different manner than that heretofore described, and the amplifier itself is of somewhat different char-.

acter. Particularly, the amplifier of the apparatus of Fig. 2 is generally of the class-B type having a grid bias set for plate current cut-off without grid excitation, all as will now be particularly described. The numeral 20a. indicates a photo-electric cell having an associated shield 22a, with the shield and photo-electric cell being connected, if desired, in a quickly releasable manner, as, for example, by the extension cord l2 and a plug and socket (not shown) to the amplifier input.

The amplifier includes the following parts connected in the manner shown: a high-mu triode, usually of the bantam type, such as a 6SF5GT, and indicated by the numeral 60; a grid biasing battery 62 of about 2 volts; a one megohm resistor 64 of the variable type, with the variability of this resistor controlling the sensitivity of the amplifier; a battery 66 of about 135 volts; a 20,000 ohm resistor 68; a small lamp bulb 10, such as a No. 40, acting as a pilot light; an amplifier tube 12 usually of the beam power type, such as a 6L6G; a battery I4 of about 22 volts for biasing the grid of the tube 12; a 6 volt battery 16 for lighting the filaments of the tubes 60, I2, and lamp l0, and for firing the fiash bul-b l8a; a battery 18, generally about 135 volts; 9. low inertia relay having a spring 82 normally holding the contacts 84 of the relay 80 together; a relay 86having a spring 88 normally tending to move the contacts 90 apart; a reset push button 92; and a fiash-on flash-off single-pull single-throw switch 94. Those skilled in the art will understand that the exact circuit constants such as above specifically recited may be varied without departing from the scope of the invention as long as the results are achieved, I

The operation of the embodiment of the appaaasaess ratus illustrated in Fig. 2 is somewhat different than the power amplification operation oi the standard amplifier already described. Particularly, in the form of the invention shown in Fig. 2, the voltage resulting from the current fiowing in the circuit including the photo-electric cell 20a and because of the light picked up by the cell 20a will overcome the grid bias of the battery 82 on the tube 60, as determined by the setting or .the sensitivity resistor 84 before there is a fiow of current in the plate circuit of the tube 88. The fiow of current in the plate circuit of the tube 60 through the resistor 68 provides voltage which overcomes the grid bias of the battery 1| on the tube 12 causing a fiow of current in the plate circuit of the tube 12 which energizes the low inertia relay 88 to break the contacts 84. when the contacts 84 are broken current flows from the battery 18 through switch 94 to the photo-flash bulb l8a, through the photo-flash bulb to fire it, back through the relay 85, the contacts 90, the filaments of the tubes 80 and 12, and lamp to the other side of the battery 16. As long asthe contacts 84 are closed the current fiows from the battery 18 through the contacts 84, the relay 88, contacts 98, the filaments of the tubes 60 and I2, and lamp 18 and back to the other side of the battery 16. In other words, the contacts 84 are positioned in the circuit to bridge or short out the flash bulb lBa, being positioned across the flash bulb so that it is not until the contacts are broken apart by the relay 80 that the firing current flows through the photo-fiash bulb l8a.

When the flash bulb I80. is fired upon the opening of the contacts 84 the firing of the flash bulb breaks the fiow of current to the relay 86 and the spring 88 causes the contacts 80 to move apart. The push button 92 is normally open so that it becomes necessary to reclose the contacts 98 of the relay 86 when it is desired to again use the apparatus. This is achieved by pushing the shorting or resetting button 92 which causes a fiow of current through the relay 86 (assuming that the contacts 84 are closed again by the spring 82 when the activating current produced by the photo-electric cell 20a has been stopped) and the circuit is thus reestablished for operation upon a second photo-fiash bulb l8 which has replaced the fired photo-fiash bulb. In order to prevent accidental operation of the photo-flash bulb iii the switch 94 is provided and this switch is closed only after the entire apparatus has been set up and is ready to be operated. The pilot light I0 indicates whether or not the filaments of the tubes 68 and 12 are energized, and also provides additional load helping to fire the photo-flash bulb.

The apparatus of Fig. 2 may be employed with the photo-electric cell aiming device as shown in Fig. 3, or the photo-electric cell without the aiming device may be mounted in association with the cabinet into which the apparatus of Fig. 2 is built, all in the manner above described. In any event, I have found that with the apparatus of Fig. 2 substantially instantaneous synchronization of firing of the flash bulb la is obtained upon the firing of a photo-flash bulb at a point remote from the photo-electric cell 20a. It will be noted in this connection that no relay is employed in the apparatus of Fig. 2 to establish or complete the firing circuit including the photofiash bulb l8a. Instead, the relay is used to bridge or short out the photo-flash bulb from the firing circuit so that a very small initial prising an amplifier,

movement of the relay 88 breaks the contacts 8| to permit a substantially instantaneous fiow oi firing current through the fiash bulb Me.

From the foregoing it will be recognized that the objects of my invention have been achieved by the provision of self-contained, relatively inexpensive, light weight, portable apparatus which is adapted to fire a photo-flash bulb in synchronism with a remotely positioned photo-flash bulb. I have found that the synchronization of firing of the photo-flash bulbs is so nearly perfect as to be entirely practical for relatively fast camera shutter speeds. The voltage of the battery 18 should not be allowed to drop below approximately volts or the necessary synchronization of the fiash bulbs in the apparatus of Fig. 2 may be impaired.

My apparatus is generally used, as will be understood, in association with a camera carrying a photo-flash bulb which is fired in synchronization with the opening of the camera shutter. The apparatus of my invention can be employed to fire one or more additional photo-flash bulbs in synchronization with the fiash bulb adjacent the camera, and at distances of as much as feet from the camera. A completely satisfactory synchronization with the first photo-flash bulb is achieved without any connecting wires of any kind between the camera and my portable apparatus.

If the aiming device shown in Fig. 3 is associated with the photo-electric cell of my improved apparatus the aiming device is, of course, pointed at the photo-flash bulb carried by the camera so that the photo-electric cell 28 or 28a will directly receive the light impulse from the first photo-flash bulb with the current produced by the photo-electric cell building up or operating through the amplifier as the intensity of the fired photo-flash bulb adjacent the camera builds up, and with the output current in the amplifier serving to fire the second photo-fiash bulb in substantial synchronization with the photo-flash bulb carried by the camera.

While in accordance with the patent statutes I have specifically illustrated and described my advance in the art, it should be particularly understood that I am not to be limited thereto or thereby, but that the scope of my invention is defined in the appended claims.

I claim:

1. Portable apparatus of the character described comprising a class B power amplifier, a photo-electric cell, adiustably positioned shielding means surrounding the photo-electric cell so that the cell can be pointed at a desired light source, variable resistance means for connecting the output of the photo-electric cell to the input grid circuit of the amplifier, a photo-flash bulb, a circuit supplying firing current to the photofiash bulb and filament current to the tubes in the amplifier, normally closed contacts shorting out the photo-flash bulb in said circuit, a low inertia relay connected to the output oi the amplifier for instantaneously opening the contacts to fire the photo-flash bulb upon the fiow of relay operating current in the output of the amplifier, a relay having normally open contacts in the firing circuit, and contact bridging means for resetting and closing the contacts of the lastnamed relay.

2. Apparatus of the character described coma photo-electric cell, variable resistance means for connecting the output 01 the photo-electric cell to the input grid circuit of the amplifier, a photo-flash bulb, a circuit supplying firing current to the photo-flash bulb, normally closed contacts shorting out the photofiash bulb in said circuit, a low inertia relay connected to the output of the amplifier for instantaneously opening the contacts to fire the photo flash bulb upon the fiow of relay operating current in the output of the amplifier, a relay having normally open contacts in the firing circuit, and contact bridging means for resetting the lastnamed relay to close the contacts thereof.

3. Apparatus of the character described comprising an amplifier, a photo-electric cell, means for connecting the output of the photo-electric cell to the input of the amplifier, a photo-flash bulb, a circuit supplying firing current to the photo-flash bulb and filament current to the tubes of the amplifier, normally closed contacts shorting out the photo-flash bulb in said circuit, a low inertia relay connected to the output of the amplifier for instantaneously opening the contacts to fire the photo-flash bulb upon the flow of relay operating current in the output of the amplifier, a relay having normally open contacts in the firing circuit, and contact bridging means for resetting the last-named relay.

4. Portable apparatus of the character described comprising a class B power amplifier, a

photo-electric cell, adjustably positioned shielding means surrounding the photo-electric cell so that the cell can be pointed at a desired light source, variable resistance means for connecting the output of the photo-electric cell to the input grid circuit of the amplifier, a photo-flash bulb, a circuit supplying firing current to the photofiash bulb, normally closed contacts shorting out the photo-flash bulb in said circuit, and a low inertia relay connected to the output of the amplifier for instantaneously opening the contacts to fire the photo-flash bulb upon the fiow of relay operating current in the output of the amplifier.

5. Apparatus of the character described comprising an amplifier, a photo-electric cell, variable resistance means for connecting the output of the photo-electric cell to the input grid circuit of the amplifier, a photo-flash bulb, a circuit supplying firing current to the photo-flash bulb, normally closed contacts shorting out the photoflash bulb in said circuit, and a low inertia relay connected to the output of the amplifier for instantaneously opening the contacts to fire the photo-flash bulb upon the flow of relay operating current in the output of the amplifier.

DONALD PARSON, JR. 

